Perception is generally held to be our primary source of knowledge. The way in which this works, however, is disputed. Some hold that perception is the occurrence of sensory ideas in the mind, which in some way reveal the nature of their external causes. Others hold that perception is a direct awareness of the external, unmediated by prior knowledge of anything internal. There is a related debate about whether sensory experience is itself conceptual. If it is not, the world is not presented to us in conceptual form; rather, we impose such a form on what we receive, by categorization or conceptualization — Professor Jonathan Dancy